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A robust "on–off" fluorescent aptasensor was developed using nanohybrids of molybdenum sulfide (MoS2) quantum dot (QD)–doped zinc metal–organic frameworks (Zn-MOF) for selective and sensitive detection of cadmium ions (Cd2+) in water. This nanohybrid (MoS2@Zn-MOF), synthesized via "bottle around the ship" methodology, exhibited a high-intensity fluorescence emission centered at 430 nm (λEm) (blue) on excitation at 320 nm (λEx). Further, the conjugation of this fluorophore to phosphate-modified cadmium aptamer (Cd-2–2) was achieved through carbodiimide reaction. The hybridization of prepared sensing probe (MoS2@Zn-MOF/Cd-2–2 aptamer) was done with dabcyl-conjugated complementary DNA (cDNA), acting as energy donor–acceptor pair in the fluorescence resonance energy transfer (FRET) system. This hybridization causes the fluorescence quenching of the nanohybrid. In the presence of Cd2+, the aptamer from the fabricated nano-biosensing probe binds to these ions, resulting in release of dabcyl-cDNA oligomer. This release of dabcyl-cDNA oligomer from the sensing probes restores the fluorescence of the nanohybrid. Under optimized conditions (sensing probe/dabcyl-cDNA ratio 1/7, pH 7.4, and temp 28 °C), the sensing probe showed a fast response time of 1 min. The fluorescence intensity of the nanohybrid can be utilized to determine the concentration of Cd2+. The proposed aptasensor achieved highly sensitive detection of Cd2+ with a limit of detection (LOD) of 0.24 ppb over the range of 1 × 10−9 to 1 × 10−4 M along with minimal effects of interferences (e.g., Hg2+, Pb2+, and Zn2+) and good reproducibility. The designed aptasensor based on MoS2@Zn-MOF nanofluorophore offers a highly sensitive and selective approach for rapid screening of metal ions in aqueous environments. [ABSTRACT FROM AUTHOR]

In the current era, catalysts have gained intensive research interest in development of sustainable energy as well as environmental remediation. Recent exploration of novel two-dimensional (2D) materials can offer unparalleled superiorities in catalysis due to their novel geometric structure and electronic properties (e.g. intrinsically anisotropic electronic, thermoelectric, mechanical, and transport properties). Phosphorene, composed of a single atomic layer of black phosphorous, has emerged as a potential single elemental 2D material that bridges the gap between 2D metal chalcogenides and graphene in terms of physical properties. The puckered structure of phosphorene imparts great potential for their catalytic applications such as the generation and storage of clean energy (e.g. photovoltaic cells, supercapacitors, lithium-ion batteries, solar water splitting, and hydrogen/oxygen evolution reactions (HER/OER). In this review, an emphasis is placed on describing phosphorene in terms of its structural features (e.g. presence of defects) and catalytic properties along with synthesis strategies (e.g. liquid phase exfoliation, mechanical exfoliation, plasma exfoliation, and electrochemical exfoliation). This review is thus expected to provide comprehensive information on the current status of phosphorene as a catalyst (e.g. photocatalyst, electrocatalyst, and thermocatalyst) based on a combination of computational and experimental results. [ABSTRACT FROM AUTHOR]

The contamination of water and food with antibiotics residues poses a severe risk to human health and aquatic environments. The excessive and uncontrolled use of antibiotics is one of the major causes of their presence in the environment. Their continuous consumption willingly or un-willingly can result in severe health issues such as allergy, headache, hypertension, muscle pain, and hormonal dysfunction. Beside these, the development of antimicrobial resistance (AMR) can make the situation more critical. Therefore, advanced analytical approaches over conventional techniques are required to detect antibiotic residues in a facile and cost-effective manner. The present work deals with the design of fluorescent nanostructures as sensing probes for the detection of ciprofloxacin. Here, we have synthesized NH2-MIL-53(Al) using a hydrothermal approach. This fluorescent metal–organic framework (MOF) was further combined with molecular imprinted polymers (MIPs) for the selective and specific detection of ciprofloxacin in aqueous solutions. The use of MIPs over other biomolecules (such as antibody, enzymes, and others) is highly promising as it avoids any kind of pre-treatment of the sample. The MIP@NH2-MIL-53(Al) nanostructure formation is confirmed by performing different characterization techniques involving both spectroscopy and microscopy. The performance of the developed fluorescent composite promotes its applicability for the highly sensitive and specific detection of ciprofloxacin in practical applications. [ABSTRACT FROM AUTHOR]

In recent years, antibiotic pollution has become a major concern due to their excessive exposure to humans and the environment. However, the existing instrument-dependent and time-consuming conventional detection approaches are not feasible for the real-time detection of antibiotics at the field level. Herein, two Cu-based metal–organic frameworks (Cu-btc) with the same stoichiometry were synthesized under different reaction conditions. The hydrothermal approach resulted in better structural and crystalline properties of Cu-btc (named as Cu-MOF2) than the preparation under normal laboratory conditions (Cu-MOF1). The high peroxidase-like activity of Cu-MOF2 was further utilized to develop a colorimetric assay for the detection of tetracycline in water. The presence of multiple O- and N-functional groups in tetracycline led the formation of tetracycline–Cu2+ complexes. Tetracycline itself did not cause any change in the color of the TMB-H2O2 system, but it could effectively hinder the colorimetric reaction of TMB with H2O2 in the presence of Cu-MOF2. The designed system demonstrated a low detection limit of 0.23 μM with a limit of quantification of 0.69 μM. The performance of this colorimetric assay was also examined in the presence of other possible interfering antibiotics. The good biocompatibility of this sensing platform increases its potential for in vitro biosensing applications. [ABSTRACT FROM AUTHOR]